Which test assesses the extrinsic coagulation pathway?

Which test assesses the extrinsic coagulation pathway?

• A. Bleeding Time
• B. PTT Test
• C. INR Test
• D. Thrombin Time

Answer: (C)

The extrinsic coagulation pathway is triggered when tissue factor is exposed and activates factor VII, with the time to clot formation largely reflected by the prothrombin time. The INR is the standardized expression of the prothrombin time, designed to be comparable across laboratories and to monitor warfarin therapy. Because it directly represents the activity of the pathway initiated by tissue factor, the INR best measures the extrinsic pathway. Bleeding time assesses platelet function, PTT evaluates the intrinsic (and common) pathway, and thrombin time looks at the final conversion of fibrinogen to fibrin, not specifically the extrinsic pathway.

The extrinsic coagulation pathway is triggered when tissue factor is exposed and activates factor VII, with the time to clot formation largely reflected by the prothrombin time. The INR is the standardized expression of the prothrombin time, designed to be comparable across laboratories and to monitor warfarin therapy. Because it directly represents the activity of the pathway initiated by tissue factor, the INR best measures the extrinsic pathway. Bleeding time assesses platelet function, PTT evaluates the intrinsic (and common) pathway, and thrombin time looks at the final conversion of fibrinogen to fibrin, not specifically the extrinsic pathway.